A Eulerian population balance/Monte Carlo approach for simulating laminar aluminum dust flames--颗粒学报PARTICUOLOGY

Sewerin, F., & Finke, J. (2024). A Eulerian population balance/Monte Carlo approach for simulating laminar aluminum dust flames. Particuology, 88, 323-343. https://doi.org/10.1016/j.partic.2023.06.007

A Eulerian population balance/Monte Carlo approach for simulating laminar aluminum dust flames

Fabian Sewerin ^*, Jannis Finke

Emmy Noether Group for Dispersed Multiphase Flows, Chair of Mechanical Process Engineering, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany

10.1016/j.partic.2023.06.007

Volume 88, May 2024, Pages 323-343

Received 20 December 2022, Revised 20 April 2023, Accepted 3 June 2023, Available online 11 July 2023, Version of Record 15 November 2023.

E-mail: fabian.sewerin@ovgu.de

Highlights

• We present a fully Eulerian methodology for simulating the combustion of aluminum dusts.

• On the population level, the dust is described in terms of a property distribution.

• Governing population balance equation is solved using a Eulerian stochastic field approach.

• Thermochemical particle-gas interaction includes evaporation, oxidation, scavenging of oxide smoke and heat conduction.

• As application, the exhaust composition of a counterflow dust flame is investigated.

Abstract

Recently, metal powders have been conceptualized as carbon-free recyclable energy carriers that may form a cornerstone of a sustainable energy economy. The combustion of metal dusts in oxidizing atmospheres is exothermal and yields oxide particles that could, potentially, be retrieved and, subsequently, recharged by conversion to pure metals using green primary energy sources. As a step towards a predictive tool for designing metal dust combustors, we present a fully Eulerian modelling approach for laminar particle-laden reactive flows that is, conceptually, based on a population balance description of the dispersed particles and relies on a stochastic Eulerian solution strategy. While the population balance equation (PBE) is formulated for the number-weighted distribution of characteristic properties among all particles near a spatial location, it is kinetically informed by the rates at which mass, momentum and heat are exchanged between the carrier gas and the particulate phase on the single particle level. Within the scope of the Eulerian Monte Carlo solution scheme, the property distribution is discretely represented in terms of the total number density and a finite number of property samples and the computational work is channelled towards the Eulerian estimation of mean particle properties.

For the case of reactive aluminum particles, we combine a kinetic description of the gas-particle heat and mass transfer with a transport-limited continuum formulation to obtain rate expressions that are valid across the entire particle size range from the free molecular through the continuum regime. Besides velocity, the particle properties include only the particle mass, temperature and oxide mass fraction. This set of thermochemical degrees of freedom is retained also as phase transitions due to melting occur, drawing on a smooth blend of the solid and liquid thermodynamic and material properties. The particle-level formulation encompasses aluminum evaporation, surface oxidation, scavenging of oxide smoke, oxide evaporation/dissociation and radiation. After investigating how these effects translate, through the PBE, to the particle population level and affect the combustion in a homogeneous dust reactor, we analyze the combustion of an aluminum dust in a counterflow flame and validate predictions of the particles’ centerline velocity profile and the flame speed by comparison with available experimental data. Concomitantly, nitrogen oxide emissions are investigated along with the particle burnout and outlet size distribution.

Graphical abstract

Keywords

Metal dust combustion; Aluminum; Population balance; Eulerian Monte Carlo

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